Background: The role of timing of retirement on cognitive functioning in old age is inconclusive so far. Therefore, the present study set out to investigate the association of timing of retirement with cognitive performance and its interplay with key correlates of cognitive reserve in a large sample of older adults. Methods: Two thousand two hundred and sixty three older adults served as sample for the present study. Different psychometric tests (Trail Making Test part A (TMT A), Trail Making Test part B (TMT B), Mill Hill) were administered. In addition, individuals were interviewed on their retirement, occupation, educational attainment, and regarding 18 leisure activities that have been carried out after retirement. Results: Earlier retirement (compared to retirement at legal age) was significantly associated with better performance in the TMT A, the TMT B, and the Mill Hill vocabulary test. Moderation analyses showed that in individuals with a moderate number of leisure activities in old age, earlier retirement was related to better cognitive performance, but not in those with a relatively large number of leisure activities. Hierarchical regression analyses revealed that entering leisure activities as additional predictor significantly increased explained variance in the cognitive measures over and above all other investigated markers of cognitive reserve (i.e. occupation and education). Conclusions: Present data further corroborate the view that leisure activities even in old age may lead to further enrichment effects and thereby may be related to better cognitive functioning. The role of engaging in activities in the context of major life events such as retirement is discussed.